Addendum: Notice the OED quote by Mrs. Delany in 1747. I've been reading out of her correspondence lately because it includes a couple of references to Sophia Carteret (author of the diary of Lady Shelburne). Seems the well-to-do had constantly fear being overturned in their sedan chairs. Sophie's diary tells a story about an acquaintance whose attendants were attacked by a drunkard while she was a-chair. On Jan. 21, 1768, Sophie wrote:

Everybody was talking of Lady Newnham's accident on the Sunday evening in her chair going from the French Ambassador's, where I had seen her. She was pursued from Soho Square to the narrow passage by Conduit Street, by a man who ran against her chair and her servants, and was several times push'd by them, once so as to be thrown down. In the passage he attack'd her first footman and stabbed him in the breast; she found herself immediately set down and surrounded by a rough mob who took the man. She went directly to her father Lord Vernon's house, where was only one woman servant, and remain'd there in the greatest distress, till the wounded man could be carried home and properly assisted. The wound appears not to be mortal, and the man who gave it to be a Mr. Ross, an attorney in the City, of good character, but very much in liquor.